Question

I have servlet to read log file my jsp call servlet at some interval.I want to add functionality in my servlet so that it read file from line next to last line from previous read.

I have following code but its not working

File file = new File("D:\\graph\\temp.log");
FileReader fr = new FileReader(file);
LineNumberReader lnr = new LineNumberReader(fr);\

lnr.setLineNumber(count)  // count is the variable keeping track of number of line  
                             previously read.

Is it need some extra code ? or is there any other alernative to do the same ?

Answer 1

From the documentation:

Note however, that setLineNumber(int) does not actually change the
current position in the stream; it only changes the value that will be
returned by getLineNumber().

Sounds to me like you’ll have to start from the beginning and call readLine in a loop until getLineNumber() is greater than count.

Something like this:

File file = new File("D:\\graph\\temp.log");
FileReader fr = new FileReader(file);
LineNumberReader lineReader = new LineNumberReader(fr);

// skip the lines you don't need 

while (lineReader.getLineNumber() < count) {
    lineReader.readLine();
}

// begin processing input here